DE102004019203B3 - Process for the gasification of storage-stable biomass to synthesis gas - Google Patents

Abstract

Process for the gasification of storage-stable biomass to synthesis gas, comprising the following process steps: rapid pyrolysis of the carbonaceous feedstocks to form pyrolysis condensate and porous pyrolysis coke particles, mixing the pyrolysis coke particles in the pyrolysis condensate to a mixture until the sedimentation is reached or exceeded in this, initiation of the mixture in a held on an overpressure entrained flow pressure carburetor and reaction of the mixture to synthesis gas under an oxygen atmosphere in the entrained-flow pressure carburetor. The object is to provide a method for the gasification of storage-stable biomass with low hazard potential in the gasification. The object is achieved by a method in which the pyrolysis coke particles have an open porosity of more than 50% and a comminution of the pyrolysis coke particles in the mixture takes place prior to introduction into the air flow pressure gasifier.

Description

The The invention relates to a process for the gasification of storage-stable Biomass to syngas according to the first Claim. The process is an integral part of a Process chain for the production of synthetic fuels and chemical raw materials from biomass and other carbonaceous materials Starting materials in general.

biomass (Waste of plant or animal origin such as animal fats, Animal meal, residual oils, but also waste oils etc.) competes with other carbonaceous feedstocks like petroleum, Natural gas and coal as energy source in the energy industry and at the same time as carbon raw material for the Chemistry. It is in contrast to the three alternatives mentioned a regenerative energy source, what they are in terms of future energy supply makes it increasingly interesting. Biomass basically includes all woody and herbaceous carbonaceous regenerative substances such as wood, straw, excrement, but also organic combustible waste.

For handling the energy source mentioned above it is beneficial if possible in fluid, i. in liquid or gaseous Form present. Consequently, there are a number of approaches that solid, awkward to handle and inhomogeneous biomass in such modifications to convert.

In the DE 101 51 054 A1 By way of example, a method for the treatment of biomass is described. The biomass is subjected to rapid pyrolysis at 400 to 600 ° C., whereby bio-oil (40 to 80% by weight) and biocokes (10 to 30% by weight) are formed. Mixing this bio-oil and pyrolysis coke produces a mixture, ie a so-called slurry (oil sludge), which is subsequently transferred into raw synthesis gas in an overflow pressure (at least 25 bar at preferably 1200 to 1800 ° C.). Here, the bio-oil and the pyrolysis coke is reacted with pure oxygen in substoichiometric ratio.

The However, this method has some significant disadvantages, which severely restrict the use of the application make special arrangements necessary.

In front all is the intermediate, the sludge (Slurry) in the mentioned Composition often not stable and storable, i.e. it is after a more or less long storage or transport time to count on a demixing. On the one hand, the Pyrolysiskoksanteil in the slurry on the other hand, the bio-oil content segregates, with an aqueous and form an organic phase. The aqueous phase may be more or less big Quantities of water-soluble contain organic compounds, in particular acetic acid, alcohols and other hydrocarbons with oxygen or other heteroatoms.

Becomes dangerous especially a locally elevated aqueous Proportion in the oil sludge, d. H. predominantly aqueous phase with only small amounts of organic phase and pyrolysis coke, during the gasification under oxygen in an airstream pressure carburetor. Rejects the watery Phase namely due to a demixing occurred a low calorific value on, i. it contains hardly combustible compounds in dissolved or dispersed form, an excess of oxygen arises in the compressed air pressure gasifier one resulting from mixing with previously generated syngas (Biogas) cause an explosion can. Unless action is taken, which impede segregation were introduced, the oil sludge immediately be further processed.

The mentioned dangers and restrictions So far, biomass utilization on a large scale is making it difficult. Especially the limit The aforementioned demixing the transport of the intermediate product, the oil sludge (Slurry) of a decentralized pyrolysis as directly as possible at the producer the biomass to a central Flugstrom- pressure carburetor for the production of biogas strong. In addition, slurries are made from seasonal waste agriculture and forestry store as intermediate for a limited time in a tank.

Also, the possibly the slurry just before the gasification to be added to mixing bio- or pyrolysis condensates in the entrained-pressure gasifier for the above reasons a serious security problem. Since the addition of mixing additional bio-oil or pyrolysis condensate must be stored in a tank partly over longer periods, there is Again, the danger that from the tank temporarily only the aqueous phase of the bio-oil is removed. The danger is especially if the tank contents can not be mixed continuously and efficiently enough.

in addition comes that the compositions of the organic and the aqueous Depending on the type of storage in the same bio-oil different phase could be, because, for example, low-boiling constituents have volatilized.

From that The invention is based on the object, a method for the gasification of storage-stable biomass without the aforementioned Disadvantages and limitations specify.

The The object is achieved by a method having the features of claim 1 solved. Preferred embodiments of the method give the dependent claims.

Of the The basic idea of the method lies in the use of an open-pore Pyrolysis coke in the mixture, which is capable of a Interference in the pyrolysis condensate or in the bio-oil of this almost completely in his pores take. The pyrolysis coke preferably has an open one Porosity of above 50%, preferably above 60% or even 75%, so that when mixing a mixture of pasty or even damp-crumbly Consistency and with a very high liq siphphasenanteil above 50, 60 or to 75% arises. The liquid ones Ingredients become practically complete and long-term stable in the open porosity stored pyrolysis, wherein the contiguous volumes of the individual Pores the liquid Partition components into sub-volumes.

A such interference is fundamental then completed when the porosity no further liquid phase absorb more. In this respect, the sedimentation density in the mixture also set or exceeded only after a certain time become. That leaves but, for example, by a slight increase in the mixing temperature (e.g., at 40 ° C) as well as by a size limit the pyrolysis coke particles (e.g., to 300 μm). Also dispersants (e.g., surfactants) as another option for this come into use.

A moist crumbly Consistency arises when the liquid phase is completely in the pores are stored only a certain residual moisture the particle surfaces the pyrolysis coke remains. By This residual moisture may cause an agglomeration of individual Particles come. Moist crumbly particles are opposite heavier in the dry state, therefore also have a higher bulk density (based on specific volume and density) and tilt in the present application in a particularly advantageous manner no more for dust formation.

at pasty Consistencies of a mixture is more liquid phase present than through the porosity of Pyrolysis Kokspartikel can be added. Unlike one Mud, e.g. Oil sludge, behave a pasty one Mixture not sedimentative, d. H. it is sediment stable. The pyrolysis coke particles remain in contact with each other and form a matrix while not in porosity bound liquid Phase through the capillary and adhesion action between the particles is bound. Pyrolysis coke is in mixtures with pasty consistencies mixed in the sedimentation density or above.

insofar is with pasty mixtures Consistency unlike, for example, sludge in a positive way not with a segregation or volatilization the liquid Phase to count.

A Mixture with the previously described high in solids integrated liquid phase component has several advantages. On the one hand, prevents the aforementioned involvement the liquid Phase in the pores leaking this, on the other hand, can cause sedimentation of the solids content in minimally unbacked liquid Phase share even with longer permanent storage are practically excluded.

A Another positive effect is through the aforementioned partitioning the liquid Ensures phase proportions, which limits the segregation of these to the respective sub-volumes and a concentration of larger quantities of watery Ingredients in the mixture makes virtually impossible and thus the beginning described explosion hazard at a gasification in the air flow pressure carburetor effectively prevented.

The aforementioned mixture present in pasty or crumbly form can, for example, be be re-liquefied in a storage or transport by the solid components (pyrolysis coke particles), for example, by a preferably wet grinding process, for example in a colloid mill, are crushed, whereby a portion of the porosity is destroyed and the incorporated therein liquid phase parts no more than integrated phase components in the mixture is present. With increasing size reduction, therefore, an increasing amount of the liquid phase portions is released for increasing liquefaction of the mixture (decreasing viscosity); the mixture thus becomes an increasingly pumpable oil sludge. This process of liquefaction may be assisted with an admixture of additional pyrolysis condensates, aqueous solutions and / or water into the mixture or by moderate heating depending on the composition and viscosity to a temperature level between 50 to 250 ° C under pressure. The time between comminution and introduction of the mixture in the compressed air pressure gasifier should, for avoiding segregation operations, not exceed 200 seconds, preferably 20 seconds. The time-dependent reduced viscosity can also be exploited by thixotropic behavior.

open-pored Pyrolysis coke with the aforementioned property profile is obtained by a rapid pyrolysis of carbonaceous feedstocks such Biomass. It is essential that in the pyrolysis one forms statistical proximity, i. a carbon matrix without regular geometry. This is mainly due to the nature of the biomass and the reaction conditions to be influenced. Mineral biomass components disturb in everyone Case the carbon skeleton and lead to misconduct. In addition will be They enriched in coke, as both pyrolysis condensate and pyrolysis gas nearly are mineral-free. High concentrations of inorganic components generally found in fast growing biomasses. These include halm-like growths like grain, but also tree bark, straw (preferably with maximum Diameter of 500 μm) or green cut annual plants like rape. The second essential Influencing factor is the reaction rate: the faster the Pyrolysis, the more disorder the coke has. Short pyrolysis times are ensured by that the biomass through 500 ° C hot sand is brought to pyrolysis. Is the temperature in the sand clear? lower, for example at only 300 ° C, would also be a pyrolysis reaction occur. As the speed of pyrolysis with temperature decreases, can be at the aforementioned comparatively low temperature also form a close order in sand (example: charcoal production). Would you the biomass at 500 ° C be called Combustion gases instead of heating up with sand, pyrolysis would also run slower, since the corresponding heat transfer is worse. Of the Heat transfer between hot Sand and the biomass particles take place at the interface of both solids. This is maximized by using a fine-grained sand fraction and the sand / biomass mixture e.g. is mechanically swirled.

• 1. Die hochporösen Pyrolysekokse sind pyrophor und beim Transport an Luft empfindlich gegen Selbstentzündung. (VCI Lagerklasse 4.2: selbstentzündliche Stoffe). Mit der vorgenannten Mischung in pastöser oder krümeliger Form lassen sich Pyrolysekokse sicher lagern und transportieren.
• 2. Im Bereich der Sedimentationsdichte und darüber ist eine sedimentationsstabile Lagerung von noch einfach förderbaren Mischungen auch ohne Stabilisator möglich.
• 3. Hochpastöse (stichfeste) Mischungen können auch nach dem sicheren Transport zu einer Zentralanlage auf eine einfacher zu pumpende und zerstäubende Feststoffkonzentration verdünnt werden.
• 4. Bei Tankleckagen oder anderen Unfällen können derartige Mischungen nicht oder nur schwer (Grenze zwischen pastös und schlammförmig) auslaufen, sich verteilen und im Boden versickern. Dadurch wird die Ausbreitung der Kontamination insbesondere von Böden durch toxische Stoffe verhindert und der weitaus größte Teil der Mischung kann wieder geborgen werden. Auch die Verdampfungsrate von brennbaren und flüchtigen toxischen Bestandteilen wird auf diese Weise drastisch reduziert. Dadurch wird eine Brand- und Explosionsgefahr deutlich vermindert.
• 5. Eine Reduktion der Viskosität der Mischung zum besseren Fördern und Zerstäuben durch Aufwärmen erfolgt unmittelbar, d.h. erst kurz vor der Vergasung durch die vorgenannte Zerkleinerung. Dadurch werden thermisch induzierte Veränderungen der Mischung während Lagerung und Transport vermieden. Die Abfallwär me aus dem Mahlprozess (Zerkleinerung) lässt sich so nützlich verwerten. Eine Viskositätsreduktion kann auch durch leichtes Verdünnen mit geeigneten flüssigen organischen Abfällen erreicht werden, für deren Entsorgung eine Gutschrift erfolgt.

With the proposed method, the following advantages can be realized, above all, in terms of safety and costs, and the transfer into a compressed air pressure gasifier can be simplified:

• 1. The highly porous pyrolysis cokes are pyrophoric and sensitive to auto-ignition when transported in air. (VCI storage class 4.2: self-igniting substances). With the aforementioned mixture in pasty or crumbly form pyrolysis coke can be stored and transported safely.
• 2. In the area of sedimentation density and above a sedimentation stable storage of still easily recoverable mixtures is possible even without stabilizer.
• 3. High-pasty mixtures can be diluted to a more easily pumped and atomized solids concentration even after safe transport to a central facility.
• 4. In the case of tank leaks or other accidents, such mixtures can not or only with difficulty (border between pasty and muddy) leak, spread and seep into the soil. This prevents the spread of contamination, in particular of soils, by toxic substances, and the vast majority of the mixture can be recovered. Also, the rate of evaporation of combustible and volatile toxic components is drastically reduced in this way. This significantly reduces the risk of fire and explosion.
• 5. A reduction in the viscosity of the mixture for better conveying and atomizing by warming takes place immediately, ie only shortly before the gasification by the aforementioned comminution. This avoids thermally induced changes in the mixture during storage and transport. The waste heat from the grinding process (comminution) can be used so useful. Viscosity reduction can also be achieved by gentle dilution with suitable liquid organic wastes, for which disposal a credit is taken.

The Invention will be described with reference to exemplary embodiments, which affect the overall process or certain process steps refer to, closer explained.

Example 1:

sedimentation density defines the point at which the solids concentration of a suspension so high is that the solid particles do not mix in a mixture settle down due to the earth gravity field. The sedimentation density depends on of porosity, true density and particle size distribution of the solid, as well as density and viscosity of the liquid. For mixtures of Pyrolysis condensate such as bio-oil and coke dust (Pyrolysis), the sedimentation density is between 20 and 35 Wt .-% solids.

By way of example, the sedimentation densities of four different pyrolysis cokes were measured by determining the solids content in the underlying bottom area of the mixture after half-yearly storage (see the following table):

The particles were sorted by size. 10% of the particles were smaller than the specified x ₁₀ value, 50% of the particles smaller than the x ₅₀ value and 90% smaller than x ₉₀ value. These values were chosen to define and record the beginning and end of the particle distribution using the x ₁₀ values and the x ₉₀ values. The x ₅₀ value is a measure of the mean particle size. The size measure used was the two-dimensional projection of the particles (statistical evaluation of an optical microscope image). Because of the better clarity not the particle area, but the equivalent circle diameter was given.

The porosity is an essential quantity for the sedimentation density, because liquid penetrates into the pore volume, without contributing to the flowability of the mixture. Empirically, it had been shown that the proportion of larger pores (> 2 μm) the flowability significantly influenced while the influence of the smaller pores (<2 μm) statistically was undetectable.

at the synthesis (rapid pyrolysis) of straw coke as pyrolysis coke a porosity between 60-90 %, with macroporosity> 2 μm alone accounting for 50-80%. The values changed in the synthesis of beechwood coke to 50-75 porosity (macroporosity> 2 μm of which 10-60%).

Example 2:

To produce 4-4.6 t of a mixture of pyrolysis tar (pyrolysis condensate) and pyrolysis coke, coke particles were ground in a continuous grinding process to the following particle spectrum using a ball mill: x ₁₀ = 1.5 μm to 4 μm, x ₅₀ = 6 μm to 30 μm, x ₉₀ = 15 μm to 120 μm. (The grain size spectrum significantly determines the mechanical properties of the mixture, while the carbon conversion degree in the entrainment gasification at> 1000 ° C irrespective of the grain size was> 99). 3.2 t pyrolysis tar were placed in a tank with stirrer and tempered to 40-60 ° C. Due to the natural gradient, the tar first ran into a 1 m ³ stirred vessel and was then pumped back into the tank. Coke was added to the stirred tar by means of a rotary valve on the mixing vessel. When dosing, it was important to ensure that a homogeneous mixture was pumped back into the tank. In order to take a ready mixture for a gasification test or a sampling a T-valve was rearranged behind the pump.

It 1400 kg of pyrolysis coke were mixed in, resulting in a solids content of 30.4%. Criterion for the maximum intended solids content here was the free flowability through the pipe and hose lines of the mixing station. Advantageous So is a dosage control over the viscosity of the mixture in the mixing vessel or in the pipeline between the mixing vessel and the stirred tank.

Example 3:

In the same apparatus as in Example 2, 3.2 t of pyrolysis vinegar (pyrolysis condensate) were heated to 20-30 ° C. The pyrolysis coke has the same grain size as in Example 2. To obtain the free flow In addition, a maximum of 2.2 t of pyrolysis coke is added (40.7% solids content in the mixture). The lower viscosity and lower density of the pyrolysis compared to Pyrolyseteer make a higher stirring and pumping capacity in the tank container necessary to avoid sedimentation during processing.

Example 4:

In a stirred tank with a stirrer, the for highly viscous materials is suitable (colloid mixer), were 3 1 pyrolysis tea filled. Subsequently was pyrolysis coke with the grain size specified in Example 2 to added to a solids content of 45%. When mixing warms up Depending on the mixing time, the slurry can reach up to 90 ° C. Criterion for the solids content In this case, the mixture was still pumpable in a hot state, however in the cold state is not freely flowable, but still one sticking thick paste above the sedimentation density) forms. This mixture proved to be particularly safe to transport, because of leaks the capillary and adhesion forces between coke and tar prevent the tar from leaking.

in the 50 g of the o.g. Mixture made with 45% solids content and absorbent on several layers Given filter paper. The mixture was not flowable. Also After 15 hours, only 1.4% of the crude tar was in the filter paper penetrated, of which alone two thirds in the uppermost position of the Filter paper. An afterthought Dilute the mixture to the fluidity restore and processing in a gasification plant was easy to achieve with a suitable stirring system.

Example 5:

In an inert stirred tank with a fast rotating stirrer, the for Whirling up of dusts is suitable, was under exclusion of air or oxygen pyrolysis coke with a grain size spectrum filled in accordance with Example 2. During the stirring process, this pyrolysis coke powder became whirled. It was about a nebulizer liquid injected, up to a composition of about 30% liquid and about 70% solids. This liquid may be formed by pyrolysis tar or pyrolysis vinegar, but also a waste fluid such as Black Liquor Pulp industry, aqueous solutions or water. The desired Solids content was about the demand, the coke completely to moisten so that he no longer dusted, but still grainy and easily recoverable was (similar a grainy Bulk material). With this low liquid content were the pores of the coke surface filled and the reactivity across from Significantly reduced atmospheric oxygen. The coke particles corresponding to a particle size spectrum Example 2 glued together to form agglomerates with one Diameter in the millimeter range (up to approx. 3 mm). The liquid content in the mix, however, was not enough to get these grains to connect a mud.

A such mixture with very high solids content offered safety the same advantages as a highly viscous described in Example 2 Mixture. At the same time it offers the advantage of being the same Easy to store, transport and process like a granular bulk material. In front Place in a gasification plant they can if necessary without problems to a sludge with lower solids content and normal liquid properties be mixed.

Example 6:

In an inert stirred tank with a fast-moving stirrer, the for Whirling up of dusts is suitable, was under air or oxygen exclusion coke powder with a grain size spectrum submitted according to Example 2. While the coke powder stirred up was handed over a nebulizer Pyrolysis tar (up to a composition of max 30% liquid and min. 70% solids). Criterion for the solids content was, that the coke is complete was wetted and no longer dusty, but was still very fine-grained (e.g., diameter about 0.5 mm). Thereafter, just as much pyrolysis vinegar is added that the mixture has sufficient conveyability Has. The advantage of this mixture is that it depends on the solids content has a Bingham rheology: Similar to ketchup is the Mix at rest not flowable and therefore has good safety properties. If she is moved, acted but they were low-viscous and settled in the airstream pressure carburetor easily pump and atomize.

Example 7

The starting materials for the pyrolysis products (pyrolysis coke and pyrolysis condensate) consisted of Contaminated biomass, eg heavy metal-containing industrial wood or straw from polluted agricultural land. Similarly, plastic-coated, ie non-compostable biomass (eg even with PVC) was also suitable. From these materials pyrolysis products were prepared and in turn the aforementioned mixtures according to Examples 2 to 6, which were reacted in the flow stream to synthesis gas.

Existing heavy metals were bound in the slag of the entrained flow gasifier and glazed (eg chromium and other heavy metals), or removed during process water purification (eg cadmium). The slag allowed a very compressed and therefore inexpensive dumping of heavy metal waste (bulk density 1200 ± 200 kg / m ³ , coarse particles <1 cm).

ever after eluate behavior and limits could even to treatment as dangerous Residual material are dispensed with. At a chlorine load of the biomass No chlorinated furans or dioxins were formed (or only at the limit of detectability), since the pyrolysis below the for the de novo synthesis necessary Temperature expires, the gas production significantly above.

Example 8:

The mixing of liquid slurries (Examples 2 and 3) was combined with the milling of the pyrolysis coke particles. Mixing and milling could be done simultaneously, for example in a pyrolysis liquid (tar or vinegar) filled ball mill, or in succession, for example by pressure crushing in a press or in rolls followed by stirring (mixing). In a discontinuous drum mill (grinding chamber dimensions 305 mm × 305 mm, 20 mm and 45 mm grinding media, grinding media / regrind ratio = 10/1), straw coke and beech wood coke were ground dry and as tar mash. The following table shows the required milling time to achieve a sieve throughput of 80% at the indicated mesh size:

In a laboratory experiment, the pressure for the comminution of straw coke and Büchenholzkoks was varied up to 562 MPa. The greater the pressure, the greater the (macro) porosity lowering of the coke. After applying a high pressure during comminution higher solids contents can be obtained with simultaneous flowability than after applying a low pressure. This is evident from the measurement results of the following two tables:

Claims (6)

Process for the gasification of storage-stable biomass to synthesis gas, comprising the following process steps: a) Rapid pyrolysis of the carbonaceous feedstocks with formation of pyrolysis condensate and porous Pyrolysis coke particles, wherein the pyrolysis coke particles open porosity above 50%, b) mixing in the pyrolysis coke particles in the pyrolysis condensate to a mixture, wherein the interference so long time until the sedimentation density reaches in the mixture or exceeded is c) Introduction of the mixture into an overpressure held air flow pressure carburetor as well d) reaction of the mixture to synthesis gas under an oxygen atmosphere in the entrained-flow gasifier, wherein e) between the interference and the initiation of a storage or a Transport of the mixture takes place as well f) a comminution the pyrolysis coke particles with a destruction of the porosity and thus a liquefaction in the mixture after storage or transport maximum 200 seconds before the introduction into the air flow pressure carburetor takes place. Method according to claim 1, characterized in that that the carbonaceous feedstocks comprise biomass and the pyrolysis condensate both organic and aqueous phase fractions contains. Method according to one of the preceding claims, characterized characterized in that the crushing a Naßmahlpro process in a colloid mill includes. Method according to one of the preceding claims, characterized characterized in that the mixture before the reaction to a temperature between 50 and 250 ° C is heated. Method according to one of the preceding claims, characterized characterized in that the interference at a temperature above 40 ° C takes place and the pyrolysis coke particles thereby have a particle size of at most 300 microns. Method according to one of the preceding claims, characterized characterized in that the mixture before entering the air flow pressure carburetor with additional Pyrolysis condensate, aqueous solutions or water is mixed.